You didn't say what car you wanted to convert, but if it is one that had a US manual version in some form, (201, 123 or 124), you can get the small parts from the dealer. That is what I concluded with my 280E conversion.

You need the big parts (transmission, linkage, flywheel, clutch disk) that are specific to the engine you are converting, but the hydraulics, pedals, etc. are the same.

What scared me the most was the possibility that the crank would be different, but at least on the 280E it is the same.